Method and apparatus for drilling and producing wells in a formation susceptible to compaction

ABSTRACT

Apparatus and method for completing a well in a subterranean oil-bearing formation wherein the well is adapted to traverse an area susceptible to compaction. A well is drilled and casing is installed in the well. The casing is provided with expansion joint means so as to prevent buckling of the casing when any compaction occurs in the area susceptible to compaction. The casing is then firmly fixed in position in the well.

c United States Patent 1 13,s93,79s

[72] Inventor Leo P. Broussard. Sr. {56] References Cited UNITED STATESPATENTS 1 "P 828,093 2,230,626 2/1941 Miller 166/242 x [22] F1lcd May19, 1969 s P d J I 20 1971 2,675,082 4/1954 Hall 166/285 Q Com 2,712,8547/1955 Creighton... 166/242 l l N k N 2,900,028 8/1959 Hanes 166/2423,020,962 2/1962 Holmquist... 166/242 3,064,729 1 1/1962 Lindley 166/297Primary Examiner-Ian A. Calvert [54 1 METHOD AND APPARATUS ron DRILLINGAND Mccamy PRODUCING WELLS IN A FORMATION EPMPACTIQN ABSTRACT: Apparatusand method for completing a well in rawmg a subterranean oil-bearingformation wherein the well is [52] U.S. Cl [66/285, adapted to traversean area susceptible to compaction. A well 166/242, 285/300, 285/301 isdrilled and casing is installed in the well The casing is pro- [51] Int.Cl ..E2lb 33/14. vided with expansion joint means so as to preventbuckling of F161 27/12 the casing when any compaction occuns in t hearea susceptible [50] Field of Search 166/285, to compaction. The casingis then flrriily'lfiited in position in the well.

A FIXED POINT URRENT) l r ZONE (F INTEREST- L-AL BOTTOM FIXED POINT 1 HFl rd PATENTEB JUL20 IIIII SHEET 1 UF 2 OP FIXED PoINT (ORIGINAL) i TOPFIXED VI POINT (CURRENT) FIG. 2

PRIOR ART PRIOR ART INVENTOR:

LEO P. BROUSSARD,SR BY:

HIS ATTORNEY PATENlEflJuLzmsn 3,593,795

SHEET 2 BF 2 L TOP FIXED POINT ORIGINAL ZONE OF INTEREST- L-AL P k H r)FIG. 4

lNVENTOR:

LEO R BROUSSARD,SR

HIS ATTORNEY METHOD AND APPARATUS FOR DRILLING AND PRODUCING WELLS IN AFORMATION SUSCEP'IIBLE TO COMPACTION BACKGROUND OF THE INVENTION 1.Field of the Invention The invention relates to well completion; and,more particularly, to amethod and apparatus for preventing buckling ofawell casing adjacent to areas susceptible to compaction.

2. Description of the Prior Art In Louisiana oil fields, certainoil-bearing formations have shown a tendency to compact aftersubstantial amounts of oil have been removed therefrom. This causessevere problems in regard to the casing and tubing in the wellsextending into these formations. In bending, the cement surrounding thewell casing cracks and sand is produced. Such bending is detrimental tothe working of such wells since it is impossible to run tools anddevices down the bent well to carry out remedial operations.

SUMMARY OF THE INVENTION It is an object of this invention to provide amethod and apparatus for preventing buckling of wells traversing areassusceptible to compaction.

It is a further object of this invention to provide apparatus which maybe readily installed in a well toprevent buckling of the casing thereofadjacent to areas susceptible to compaction.

These objects are preferably carried out by completing a well into anarea susceptible to compaction. The well is cased and the casing isprovided with expansion joint means so as to prevent buckling of thecasing when any wheel of the formation traversed by the well occurs. Thecasing is then firmly fixed in the well. In a preferred embodiment, theexpansion joint means includes a high pressure seal element.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a vertical sectional, partlyschematic, view of a well in accordance with the teachings of thepresent invention;

FIG. 2 is a vertical sectional, partly schematic, view of the well ofFIG. I subject to buckling;

FIG. 3 is a vertical sectional, partly schematic, view of the well ofFIG. I wherein the well casing is provided with expan' sion joint meansin accordance with the teachings of the present invention; and

FIG. 4 is a vertical, partly sectional, view of the expansion jointmeans of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, FIG. 1shows a well borehole I extending into a subterranean oil-bearingformation II. Well borehole includes a casing 12 cemented therein bycementing, as at 13. Well borehole 10 may also include atubing string 14and a packer 15 as is well known in the art for working well borehole10. The well casing I2 mayalso be perforated with perforations 16extending through casing I2, cement I3 and into formation 11, as is alsowell known in the art.

Oil-bearing formation 1] may, for example, be divided into an uppersand-shale area 17, a lower shale area I8, a still lower sand area I9and a bottom shale area 20. For the purposes of this discussion, it willbe assumed that oil-sand area 19 is highly susceptible to compaction. Asillustrated in FIG. 1, the zone of interest, i.e., the area in which anybuckling of casing 12 is likely to occur due to sand compaction,comprises a top fixed point adjacent to shale area I8 and a bottom fixedpoint adjacent to the bottom of sand area I9. Thus, axial load on casingI2, prior to production, is substantially negligible.

Referring now to FIG. 2, after production of well borehole 10 throughperforations I6 and up tubing string 14 past packer 15, a significantamount of compaction of the sand in the oil-sand area 19 has takenplace. Thus, as can be seen in Fig. 2, casing I2, cement l3 and tubing;string I4 show a serious amount of buckling adjacent to sand area 19.The axial load on casing 12 is high, in the order of, for example,560,000 to l,l00,000 pounds. The top fixed point has shifted by anamount AL to a lower fixed point. Due to the axial loads on casing I2,casing deformation takes place. Such deformation renders the futureworking within well borehole 10 very difficult and expensive.

Such casing buckling may be prevented by cutting a section of thecemented casing l2 adjacent to the sand area I9 by means of pipe cuttersor the like, well known in the art. The cut section of the casing 12 maybe so cut as to destroy it for all practical purposes so that the cutpieces fall to the bottom of well borehole I0. This results inshortening the pipe string or casing in the area of compaction, thusrelieving the axial stress on casing I2. After cutting, an internalsleeve may be installed between the horizontally cut sections of casing12; alternatively, the cutaway portion may be otherwise sealed such asby injection of epoxy resin or other suitable sealing means.Nevertheless, the above operation is expensive and alignment of the twocasing sections may be difficult once the casing I2 is cut or destroyed.In addition, sand consolidation of sand area 19 is limited and in somecases may be impossible once the casing 12 is destroyed.

Preferably, however, in accordance with the teachings of the presentinvention, formation II is logged by techniques well known in the art soas to determine the upper and lower limits of sand area 19, i.e., thepotentially productive zone. At the places in casing I2 adjacent tothese upper and lower limits, or at least adjacent to the interval to beperforated, slip couplings in accordance with this invention arepreferably installed, as illustrated in FIG. 3. Thus, a first slipcoupling 21 is shown disposed adjacent to the base of sand area 19.

Although two such slip couplings are shown in FIG. 3, obviously one ormore couplings may be installed in the well casing I2 within the wellborehole 10. Also, as. is well known in the art, short sections in astring of pipe or casing, known as subs," may be installed in a wellcasing. Here, the sub" is the slip coupling which, as will be discussedfurther hereinbelow with reference to FIG. 4, is a telescoping sectionin the casing 12. The subs" (i.e., couplings 2I and 22) are disposedadjacent to sand area 19 which is susceptible to compaction. Ifnecessary to assure the proper location ofcouplings 21 and 22 in thewell borehole I0 with respect to the productive zone or zones, such assand area 19, a collar locator log, as is well known in the art, may betaken prior to cementing the casing I2 in place. After the appropriateslip coupling or couplings are installed, casing I2 is cemented and theproductive zones, such as sand area I9, are perforated in a conventionalmanner, as at perforations I6 with appropriate sand consolidationtechniques being applied, where applicable. Pattern perforating for usewith more sophisticated sand consolidation placement tools may beeffected in a conventional manner as the coupling or couplings do notreduce drift through the casing 12. Thus, as seen in FIG. 3, axial loadsinduced on casing 12 by compaction of sand area I9 between fixed casingpoints and by packer forces and/or other forces associated withconventional oil well production practices, are absorbed by slipcouplings such as couplings 2ll and 22, thus precluding buckling ofcasing 12. Although only one such sand area susceptible to compactionhas been shown, obviously a plurality of such vertically spaced areas orstrata may be traversed by well borehole 10 with appropriate slipcouplings installed as required.

Referring now to FIG. 4, a slip coupling in accordance with theteachings of this invention is illustrated. Obviously, all the slipcouplings may be similar to slip coupling 21 illustrated in FIG. 4 anddescribed hereinbelow.

Slip coupling 211 includes an inner :member 23 slidably mounted in anouter member 24. Thus, member 23 telescopes into member 24. The upperend of inner member 23 includes a threaded portion 25 for connectingcoupling 21 to a stan dard casing coupling (not shown). In like manner,the lower end of outer member 24 includes a like threaded portion 26 forconnecting coupling 21 to a standard casing coupling (not shown). inthis manner, the slip coupling 2K may be connected at any desiredlocation in casing 12.

lnner member 23 includes an outer circumferential skirt portion such ascylinder 27, preferably of steel or similar material adapted to extenddownwardly into a chamber 28, also preferably of steel, extendingcircumferentially of outer member 24. Cylinder 27 may be threaded ontothe outer wall of inner member 23 as indicated by threads 29;alternatively, cylinder 27 may be integral with inner member 23, ifdesired. In either case, the outer surface of cylinder 27, adapted toslide downwardly into chamber 28, is coated to prevent cement bonding ofthe inner member 23 in chamber 28. Suitable coating materials mayinclude a pliable rubber sleeve, rubber base material, etc.

A slot 30 extends longitudinally of cylinder 27. A pin 31 fixed inposition in chamber 28 is adapted to slidably engage slot 30 so as toprevent rotation and/or premature movement of inner member 23 withrespect to outer member 24. Obviously, a plurality of such pins andmating slots may extend circumferentially of chamber 28 and cylinder 27,respectively.

The upper movement of cylinder 27 with respect to chamber 28 is limitedby stop means 32 on cylinder 27,

adapted to engage mating stop means 33 in chamber 28. A plurality ofO-rings seal cylinder 27 and chamber 28 so as to exclude'debris from thecoupling 21. If desired, chamber 28 may comprise an integral member, or,as shown in FIG. 4, be formed of sections threaded to outer member 24 asat threads 34 and 35, respectively, to form an integral chamber forcylinder 27.

A bellows 36 is disposed in chamber 28, fixed at one end 37 by brazingor other means well known in the art on cylinder 27 and the other end 38to an abutment wall 39 disposed at the lower end or bottom of chamber28. Bellows 36 provides a pressure seal between inner member 23 andouter member 24. Bellows 36 is preferably ofa thin-walled multi-plymaterial resistant to corrosion, such as Monel metal. The sealed bellowschamber, that is, the portion of chamber 28 between cylinder 27 andabutment wall 39, is preferably filled with a noncompressible fluid,such as oil, to prevent well bore fluids such as mud or cement fromobstructing bellows movement and to lubricate the cylinder and chamberwalls.

A pair of valve chambers 40 and 4B are disposed below abutment wall 39.Ports 42 and 43, respectively, lead from the bellows chamber to therespective chambers 40 and 41. Spring-loaded check valves are disposedin chambers 40 and 41, respectively, with springs 46 and 47,respectively, fixed at one end to their respective valve and the otherend to the bottom wall of their respective chambers. Relief ports 48 and49 are formed in chambers 40 and 41, respectively, for allowingdisplacement of the noncompressible chamber fluid when movement ofcasing 23 occurs due to axial loading as disc usmed hereinabove.

Conventional piston-type equalizers, such as equalizer 50, to providefor the internal pressure within the bellows chamber are preferablydisposed in an equalizer chamber 51 below abutment wall 39. An outletport 52 connects chambers 51 with the inner bellows chamber and an inletport 53 is disposed at the lower end of the chamber 51. A similararrangement is utilized to provide for the external pressure within thebellows chamber. in this equalizer chamber (identical to 51 except forports) an outlet port 61 connects the equalizer chamber with the outerbellows chamber and an inlet port 60 is disposed at the lower end of theequalizer chamber. The purpose of the pressure equalizer is to equalizethe pressure on either side of the bellows with respective pressuresoutside and inside the casing 24 without allowing external fluid, suchas cement, to enter the seaied bellows chamber.

Thus, in operation, as illustrated in FIG. 3 and discussed hereinabove,as axial load is placed on casing 12 as a result of compaction of thesand in sand area 19, slip couplings 21 and 22, previously installed incasing 12 by means of threads 25 and 26, respectively, provide amechanical means for relieving axial loads on casing 112, thus providinga maximum chance for sand consolidation and a minimum chance forcomplicated and expensive workovers, especially offshore, associatedwith casing deformation due to buckling.

Thus, as the casing H2 is disposed to buckle due to axial stress, innermember 23 of slip coupling 2] telescopes downwardly into outer member 24while maintaining a seal therebetween due to O-rings 34. Pin or pins 3islide in a slot or slots 31, thereby preventing rotation and/orpremature movement between members 23 and 24. Bellows 36 provides a highpressure seal, thereby permitting installation of like couplingsopposite all potentially productive zones in formation l1 along with aminimum chance of easing leakage. Such a leakproof connection in aproducing zone is important so as to prevent excessive gas productionfrom the top of the producing zone and water production from the base ofthe producing zone. Check valves 44 and 45, along with equalizer 50,provide an appropriate integral relief system allowing displacement ofthe noncompressible chamber fluid when casing movement occurs.

In summary, the slip couplings of the present invention, properlyinstalled in well casing, provide casing relief with minimum resistanceadjacent to formations susceptible to compaction. The external coatingof the upper cylinder 27 prevents cement adhesion and the oil-filledsealed-bellows chamber excludes cement and other foreign material. Thelow resistance to movement offered by the bellows 36, preferablymulti-ply, and the oil-lubricated cylinder and chamber walls insuresminimum resistance to movement with maximum relief of axial casingloads.

I claim as my invention:

I. A method of drilling and completing a well in a subter raneanoil-bearing formation wherein at least a portion of said formation issusceptible to formation compaction, the method comprising the steps of:

drilling a well into said formation traversing the portion susceptibleto compaction;

installing a well casing in said well;

providing said well casing with joint means adjacent to said portionsusceptible to compaction adapted to move from an expanded state to acontracted state relative to changes in compaction of said portion thuspreventing buckling of said casing when any compaction occurs in saidportion of the formation susceptible to compaction, said joint meansbeing installed in said well casing in substantially its expanded state;

coating at least a portion of said joint means with a material adaptedto prevent said portion from adhering to a material to be used to cementsaid casing in said well; and thereafter cementing said casing firmly inposition in said well with cement around said coated portion of saidjoint means.

2. The method of claim 1 wherein the step of providing said well casingwith joint means includes providing said casing with at least one ofsaid joint means disposed adjacent to substantially the top of theportion susceptible to compaction and at least one of said joint meansdisposed adjacent to substantially the bottom of the portion susceptibleto buckling.

3. Apparatus for preventing buckling of a well casing in a wellextending into a subterranean oil-bearing formation wherein a least aportion of said formation is susceptible to formation compaction, theapparatus comprising:

a well casing cemented in fixed position in said well adjacent to theportion of said formation susceptible to compaction; and

joint means disposed in said casing adjacent to the portion of saidformation susceptible to compaction adapted to move from an expandedstate to a contracted state relative to changes in compaction of saidportion thus preventing buckling of said casing when any compactionoccurs in said portion susceptible to compaction, said joint means beingdisposed in said casing in substantially its expanded state, said jointmeans including an inner member telescopingly received in an outermember in a fluidtight relationship, the inner member having firstconnecting means at its outer end for coupling to a first portion ofsaid well casing and the outer member having second connecting means atits outer end for coupling to a second portion of said well casing, stopmeans disposed on at least one of said members for preventing theseparation of said members, and a chamber containing a bellows meansthat is interconnected between said inner and outer members for pressuresealing said members.

4. The apparatus of claim 3 wherein said bellows chamber is filled witha noncompressible fluid adapted to prevent extraneous fluids fromobstructing the movement of said he! walled, multi-ply bellows and saidnoncompressible fluid is an oil.

7. The apparatus of claim 3 wherein the outer surface of said innermember is coated with a material adapted to prevent adhesion of saidinner member to said cemented portion of said formation traversed bysaid well.

1. A method of drilling and completing a well in a subterraneanoil-bearing formation wherein at least a portion of said formation issusceptible to formation compaction, the method comprising the steps of:drilling a well into said formation traversing the portion susceptibleto compaction; installing a well casing in said well; providing saidwell casing with joint means adjacent to said portion susceptible tocompaction adapted to move from an expanded state to a contracted staterelative to changes in compaction of said portion thus preventingbuckling of said casing when any compaction occurs in said portion ofthe formation susceptible to compaction, said joint means beinginstalled in said well casing in substantially its expanded state;coating at least a portion of said joint means with a material adaptedto prevent said portion from adhering to a material to be used to cementsaid casing in said well; and thereafter cementing said casing firmly inposition in said well with cement around said coated portion of saidjoint means.
 2. The method of claim 1 wherein the step of providing saidwell casing with joint means includes providing said casing with atleast one of said joint means disposed adjacent to substantially the topof the portion susceptible to compaction and at least one of said jointmeans disposed adjacent to substantially the bottom of the portionsusceptible to buckling.
 3. Apparatus for preventing buckling of a wellcasing in a well extending into a subterranean oil-bearing formationwherein a least a portion of said formation is susceptible to formationcompaction, the apparatus comprising: a well casing cemented in fixedposition in said well adjacent to the portion of said formationsusceptible to compaction; and joint means disposed in said casingadjacent to the portion of said formation susceptible to compactionadapted to move from an expanded state to a contracted state relative tochanges in compaction of said portion thus preventing buckling of saidcasing when any compaction occurs in said portion susceptible tocompaction, said joint means being disposed in said casing insubstantially its expanded state, said joint means including an innermember telescopingly received in an outer member in a fluidtightrelationship, the inner member having first connecting means at itsouter end for coupling to a first portion of said well casing and theouter member having second connecting means at its outer end forcoupling to a second portion of said well casing, stop means disposed onat least one of said members for preventing the separation of saidmembers, and a chamber containing a bellows means that is interconnectedbetween said inner and outer members for pressure sealing said members.4. The apparatus of claim 3 wherein said bellows chamber is filled witha noncompressible fluid adapted to prevent extraneous fluids fromobstructing the movement of said bellows.
 5. The apparatus of claim 4wherein at least one of said members includes fluid relief means forallowing displacement of the noncompressible chamber fluid when saidinner member moves with respect to said outer member.
 6. The apparatusof claim 4 wherein said bellows is a thin-walled, multi-ply bellows andsaid noncompressible fluid is an oil.
 7. The apparatus of claim 3wherein the outer surface of said inner member is coated with a materialadapted to prevent adhesion of said inner member to said cementedportion of said formation traversed by said well.